Although in sub-rule (2) no authority has been mentioned to whom a written defence has to be submitted, the written defence has to be submitted to the enquiry officer appointed to held the enquiry.
Chairman, Power Development Board, Dhaka and others v. Md. Faziul Haque, 22 BLD (AD) 85.

Power Development Board (Employees) Service Rules, 1932
Rule 143—
In view of rule 143(1)(2) of the Power Development Board (Emplo­yees) Service Rules, 1982, the High Court Division erred in law in holding that the respondent is entitled to get another show cause notice by the authority to submit written defence to them as per sub-rule (2) of rule 143 and that not having been given there was gross violation of the said rule.) But in the facts and circumstances of the case the factual aspect of the case having been found in favour of the respondent as elaborately discussed by the High Court Division holding that factually there is no justification for imposing any penalty on the respondent, in order to secure the interest of justice and do complete justice the impugned judgment warrants no interference. Chairman, Power Development Board vs Md Fazlul Hague 7 BLC (AD) 122.

Reinstate in the service of the PDB– The writ petitioners under the Bangladesh Power Development Board (PDB) keeping the writ petitioners service with the West Zone Power Distribution Company Limited (herein after referred to as "WZPDCL") on lien under the Bangladesh Power Development Board (PDB)–
From the said notification dated 22-11-2007 it also appears that PDB withdrew the decision of asking for option from the employees and officers working in "WZPDCL" on lien from PDB either to remain in WZPDCL or to return to PDB rather it informed that the lien would not be extended any further after 15-12-2007. In that case the employees working with "WZPDCL" on lien from PDB would be treated as employees of "WZPDCL" upon executing agreements. This exercise of option of returning back to PDB was condition precedent inasmuch as signing of an agreement. In the said notification it was cautioned that those who would not enter into any agreement they would go on retirement upon receiving their salaries and benefits as per their entitlements and PDB would bear the entire expenses of the same. Further condition was that those who would enter into agreement to remain with "WZPDCL" all their expenses would be born in by "WZPDCL". This option is also condition precedent. If anyone did not enter into any agreement within the time fixed they would not be entitled to be treated as employees of PDB. Section 151A of the gazette notification dated 29-12-2002 has clearly spelt out as to when the employees of PDB are to be treated as resigned employees and how their resignations would be accepted and how they would be released from the service of the Board. The present respondents admittedly had been working as employees of WZPDCL. Though they claim that they filed application for returning to the service of PDB but they failed to establish such claim. …Bangladesh Power Development Board (PDB) =VS= Bablu Kumar Chaubay, (Civil), 2019 (2) [7 LM (AD) 352] ....View Full Judgment